textproduct: Rapid City

KEY MESSAGES

- Unsettled and cool weather this weekend - Frost possible northeastern WY plains Sunday morning - Warming trend next week

UPDATE

Issued at 932 PM MDT Fri Jun 12 2026

Upper impulse and associated jet streak starting to force some precip over far NW SD this evening. System is on track to support rain across NE WY and far western SD Sat, with below normal temps as highs top out in the 50s and low 60s there. Warmer and dry for the remainder of the FA Sat, with mainly 70s expected toward central SD. Breezy across much of the SD Plains Sat, esp nw SD. Cool and dry conds expected Sat night wight winds becoming light. This will allow temps to fall into 40s most areas with 30s expected in NE WY. The higher elevations of the BH will see even cooler temps with some upper 20s expected in valleys and low spots. Expect frost where temps fall into the 30s or below across the BH and northeast WY. Warming up next week gradually with spotty chances for rain toward the end of the week.

DISCUSSION

(This Evening Through Friday) Issued at 142 PM MDT Fri Jun 12 2026

19z surface analysis had weak trough over the CWA with a frontal boundary across northern MT/ND. Water vapour loop had mean trough over central Canada with next shortwave trough of interest over southern AB/northwest MT, currently conjuring some shra/TS. Few CU over the CWA. Main concern this forecast is upstream shortwave trough.

Tonight/Saturday, shortwave trough slips east/southeast along frontal boundary. Nice band of 800-600mb frontogenesis sets up behind front tapping into limited moisture. Should see a band of showers over southeast MT/northeastern WY later tonight (probably poking into far western SD), peaking Saturday morning. Synoptic support quickly ends midday Saturday, allowing QPF band to dissipate. Gusty northwest winds expected on the SD plains Saturday given boundary layer flow/mixing. Temperatures tonight/Saturday near guidance.

Clearing skies and slackening wind Saturday night may lead to frost over northeastern WY plains Sunday morning. Will let later shifts take a look at potential headlines.

Looking ahead to next week, most guidance suggests slow expansion of upper/thermal ridge into the northern plains, but we'll still be under northwest flow aloft with potential for moisture-starved weak disturbances/fronts and even perhaps a smattering of PoPs. Overall general trend will be warmer/drier, however.

AVIATION

(For the 12Z TAFS Through 12Z Sunday Morning) Issued At 521 AM MDT Sat Jun 13 2026

Rain showers along with MVFR/IFR ceilings will continue across northeastern WY (including KGCC) and the Black Hills through this morning. Confidence is low that showers and lowered flight conditions will impact KRAP. Expect VFR conditions to persist outside of these areas across the western SD plains into central SD. Conditions overall will improve to VFR after ~21z.

UNR WATCHES/WARNINGS/ADVISORIES

SD...None. WY...None.